RDMA/mlx5: Rework implicit ODP destroy

Use SRCU in a sensible way by removing all MRs in the implicit tree from
the two xarrays (the update operation), then a synchronize, followed by a
normal single threaded teardown.

This is only a little unusual from the normal pattern as there can still
be some work pending in the unbound wq that may also require a workqueue
flush. This is tracked with a single atomic, consolidating the redundant
existing atomics and wait queue.

For understand-ability the entire ODP implicit create/destroy flow now
largely exists in a single pair of functions within odp.c, with a few
support functions for tearing down an unused child.

Link: https://lore.kernel.org/r/20191009160934.3143-13-jgg@ziepe.ca
Reviewed-by: Artemy Kovalyov <artemyko@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h
index 88769fcffb5a..b8c958f62628 100644
--- a/drivers/infiniband/hw/mlx5/mlx5_ib.h
+++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h
@@ -618,10 +618,13 @@ struct mlx5_ib_mr {
 	u64			pi_iova;
 
 	/* For ODP and implicit */
-	atomic_t		num_leaf_free;
-	wait_queue_head_t       q_leaf_free;
-	atomic_t		num_pending_prefetch;
+	atomic_t		num_deferred_work;
 	struct xarray		implicit_children;
+	union {
+		struct rcu_head rcu;
+		struct list_head elm;
+		struct work_struct work;
+	} odp_destroy;
 
 	struct mlx5_async_work  cb_work;
 };